Let's say we have a html string like "2 < 4"
How should be determined if it contains any of these extended sequences?
I 've found HTML::Entities on CPAN, but it doesn't provide 'check' method.
Details: fixing 'truncate' method in a way to not leave corrupted string like "2 &l" and not to do unnecesary work. It should look like this
$s = HTML::Entities::decode_entities ($s) if $has_ext_chars;
$s = substr ($s, 0, $len - 3) . '...' if length $s > $len;
$s = HTML::Entities::encode_entities ($s, "‚„-‰‹‘-™›\xA0¤¦§©«-®°-±µ-·»") if $has_ext_chars;
How do I determine $has_ext_chars?
A complete list of character entities can be found on the W3C reference.
You have also to match \&#u?\d+; and \&#x[a-fA-F0-9]+;
From perldoc HTML::Entities:
The module can also export the
%char2entity and the %entity2char
hashes, which contain the mapping from all characters to the
corresponding entities (and vice versa, respectively).
You can probably use them to build regexes. For example, to match entities:
use HTML::Entities '%entity2char';
my $regex = "&(?:" . join("|", map {s/;\z//; $_} keys %entity2char) . ");";
if ($str =~ /$regex/) {
print "$str contains entities\n";
}
This will skip entities like &#entity_number; though.
You can try it with a regular expression
$str =~ /.*\&[^\s]+;.*/
From your code sample you have probably just introduced a cross site scripting attack into your application. If I were to get your code to process something like <script src="evil.example.com"></script> your code would decode it to valid HTML and not re-encode the < and > back to entities. (The angle brackets in the code are not ASCII angle brackets.)
If you are truncating a string that contains any HTML tags or entities you will probably break something if you use a simple solution. You might be better off building a solution based on an HTML parsing module. If you are only looking at text inside an element with no elements inside it you can grab the text, truncate it and then replace it back into the element. If you have to deal with mixed content it will be more complicated.
But in the interest of bad solutions:
#treats each entity as one character "2 < 4" is 5 characters long
$trunc_len = $len - 3;
$str =~ s/^((?>(?:[^&]|&[^\s;]+;?){$trunc_len}))(?:[^&]|&[^\s;]+;?){4,}/$1.../;
#abuses proceadural nature of the regexp engine
#treats each input character as on character "2 < 4" is 8 characters long
$str =~ s/^( (?:[^&]|&[^\s;]+;?)+ )(?(?{ $found = (pos() > ( $found ? $len - 3 : $len ))})(?!)).*$(?(?{pos() < $len })(?!))/$1.../x;
Both are fairly permissive in what is an entity to allow for common browser quirks.
Related
I'm using Perl to feed data to an LCD display. The display is 8 characters wide. The strings of data to be displayed are always significantly longer than 8 characters. As such, I need to break the strings down into "frames" of 8 characters or less, and feed the "frames" to the display one at a time.
The display is not intelligent enough to do this on its own. The only convenience it offers is that strings of less than 8 characters are automatically centered on the display.
In the beginning, I simply sent the string 8 characters at a time - here goes 1-8, now 9-16, now 17-24, etc. But that wasn't especially nice-looking. I'd like to do something better, but I'm not sure how best to approach it.
These are the constraints I'd like to implement:
Fit as many words into a "frame" as possible
No starting/trailing space(s) in a "frame"
Symbol (ie. hyphen, ampersand, etc) with a space on both sides qualifies as a word
If a word is longer than 8 characters, simulate per-character scrolling
Break words longer than 8 characters at a slash or hyphen
Some hypothetical input strings, and desired output for each...
Electric Light Orchestra - Sweet Talkin' Woman
Electric
Light
Orchestr
rchestra
- Sweet
Talkin'
Woman
Quarterflash - Harden My Heart
Quarterf
uarterfl
arterfla
rterflas
terflash
- Harden
My Heart
Steve Miller Band - Fly Like An Eagle
Steve
Miller
Band -
Fly Like
An Eagle
Hall & Oates - Did It In A Minute
Hall &
Oates -
Did It
In A
Minute
Bachman-Turner Overdrive - You Ain't Seen Nothing Yet
Bachman-
Turner
Overdriv
verdrive
- You
Ain't
Seen
Nothing
Yet
Being a relative Perl newbie, I'm trying to picture how would be best to handle this. Certainly I could split the string into an array of individual words. From there, perhaps I could loop through the array, counting the letters in each subsequent word to build the 8-character "frames". Upon encountering a word longer than 8 characters, I could then repetitively call substr on that word (with offset +1 each time), creating the illusion of scrolling.
Is this a reasonable way to accomplish my goal? Or am I reinventing the wheel here? How would you do it?
The base question is to find all consecutive overlapping N-long substrings in a compact way.
Here it is in one pass with a regex, and see the end for doing it using substr.
my $str = join '', "a".."k"; # 'Quarterflash';
my #eights = $str =~ /(?=(.{8}))/g;
This uses a lookahead which also captures, and in this way the regex crawls up the string character by character, capturing the "next" eight each time.
Once we are at it, here is also a basic solution for the problem. Add words to a buffer until it would exceed 8 characters, at which point it is added to an array of display-ready strings and cleared.
use warnings;
use strict;
use feature 'say';
my $str = shift // "Quarterflash - Harden My Heart";
my #words = split ' ', $str;
my #to_display;
my $buf = '';
foreach my $w (#words) {
if (length $w > 8) {
# Now have to process the buffer first then deal with this long word
push #to_display, $buf;
$buf = '';
push #to_display, $w =~ /(?=(.{8}))/g;
}
elsif ( length($buf) + 1 + length($w) > 8 ) {
push #to_display, $buf;
$buf = $w;
}
elsif (length $buf != 0) { $buf .= ' ' . $w }
else { $buf = $w }
}
push #to_display, $buf if $buf;
say for #to_display;
This is clearly missing some special/edge cases, in particular those involving non-word characters and hyphenated words, but that shouldn't be too difficult to add.†
Here is a way to get all consecutive 8-long substrings using substr
my #to_display = map { substr $str, $_, 8 } 0..length($str)-8;
† Example, break a word with hyphen/slash when it has no spaces around it (per question)
my #parts = split m{\s+|(?<=\S)[-/](?=\S)}, $w;
The hyphen/slash is discarded as this stands; that can be changed by capturing the pattern as well and then filtering out elements with only spaces
my #parts = grep { /\S/ } split m{( \s+ | (?<=\S) [-/] (?=\S) )}x, $w;
These haven't been tested beyond just barely. Can fit in the if (length $w > 8) branch.
The initial take-- The regex was originally written with a two-part pattern. Keeping it here for record and as an example of use of pair-handling functions from List::Util
The regex below matches and captures a character, followed by a lookahead for the next seven, which it also captures. This way the engine captures 1 and 7-long substrings as it moves along char by char. Then the consecutive pairs from the returned list are joined
my $str = join '', "a".."k"; # 'Quarterflash';
use List::Util qw(pairmap);
my #eights = pairmap { $a . $b } $str =~ /(. (?=(.{7})) )/gx;
# or
# use List::Util qw(pairs);
# my #eights = map { join '', #$_ } pairs $str =~ /(.(?=(.{7})))/g;
$text = "I like apples more than oranges\n";
#words = split /” “/, $text;
foreach (#words) [1..] {
if $words "AEIOUaeiou";
$words =~ tr/A E I O U a e i o u//d;
}
print "$words\n";
"I like apples more than oranges" will become "I lk appls mr thn orngs". "I" in "I", "a" in "appls" and "o" in "orngs" will stay because they are the first letter in the word.
This is my research assignment as a first year student. I am allowed to ask questions and later cite them. Please don't be mean.
I know you say you are not allowed to use a regex, but for everyone else that shows up here I'll show the use of proper tools. But, then I'll do something just as useful with tr///.
One of the tricks of programming (and mathematics) decomposing what look like hard problems into easier problems, especially if you already have solutions for the easy problems. (Read about Parnas decomposition, for example).
So, the question is "How can I remove all the vowels unless they are in word beginnings?" (after I made your title a bit shorter). This led the answers to think about words, so they split up the input, did some work to ensure they weren't working on the first character, and then reassembled the result.
But, another way to frame the problem is "How do I remove all the vowels that come after another letter?". The only letter that doesn't come after another letter is the first letter of a word.
The regex for a vowel that comes after another letter is simple (but I'll stick to ASCII here, although it is just as simple for any Unicode letter):
[a-z][aeiou]
That only matches when there is a vowel after the first letter. Now you want to replace all of those with nothing. Use the substitution operator, s///. The /g flag makes all global substitutions and the /i makes it case insensitive:
s/[a-z][aeiou]//gi;
But, there's a problem. It also replaces that leading letter. That's easy enough to fix. The \K in a substitution says to ignore the part of the pattern before it in the replacement. Anything before the \K is not replaced. So, this only replaces the vowels:
s/[a-z]\K[aeiou]//gi;
But, maybe there are vowels next to each other, so throw in the + quantifier for "one or more" of the preceding item:
s/[a-z]\K[aeiou]+//gi;
You don't need to care about words at all.
Some other ways
Saying that a letter must follow another letter has a special zero-width assertion: the non-word boundary, \B (although that also counts digits and underscore as "letters"):
s/\B[aeiou]+//gi;
The \K was introduced v5.10 and was really a nifty trick to have a variable-width lookbehind. But, the lookbehind here is fixed width: it's one character:
s/(?<=[a-z])[aeiou]+//gi;
But, caring about words
Suppose you need to handle each word separately, for some other requirement. It looks like you've mixed a little Python-ish sort of code, and it would be nice if Perl could do that :). The problem doesn't change that much because you can do the same thing for each individual word.
foreach my $word ( split /\s+/, $x ) {
.... # same thing for each word
}
But, here's an interesting twist? How do you put it all back together? The other solutions just use a single space assuming that's the separator. Maybe there should be two spaces, or tabs, or whatever. The split has a special "separator retention mode" that can keep whatever was between the pieces. When you have captures in the split pattern, those capture values are part of the output list:
my #words_and_separators = split /(\s+)/, $x;
Since you know that none of the separators will have vowels, you can make substitutions on them knowing they won't change. This means you can treat them just like the words (that is, there is no special case, which is another thing to think about as you decompose problems). To get your final string with the original spacing, join on the empty string:
my $ending_string = join '', #words_and_separators;
So, here's how that might all look put together. I'll add the /r flag on the substitution so it returns the modified copy instead of working on the original (don't modify the control variable!):
my #words;
foreach my $word ( split /(\s+)/, $x ) {
push #words, $word =~ s/\B[aeiou]+//gr;
}
my $ending_string = join '', #words;
But, that foreach is a bit annoying. This list pipeline is the same, and it's easier to read these bottom to top. Each thing produces a list that flows into the thing above it. This is how I'd probably express it in real code:
my $ending_string =
join '',
map { s/\B[aeiou]+//gr } # each item is in $_
split /(\s+)/, $x;
Now, here's the grand finale. What if we didn't split thing up on whitespace but on whitespace and the first letter of each word? With separator retention mode we know that we only have to affect every other item, so we count them as we do the map:
my $n = 0;
my $ending_string =
join '',
map { ++$n % 2 ? tr/aeiouAEIOU//dr : $_ }
split /((?:^|\s+)[a-z])/i, $x;
But, I wouldn't write this technique in this way because someone would ultimately find me and exact their revenge. Instead, that foreach I found annoying before may soothe the angry masses:
my $n = 0;
foreach ( split /((?:^|\s+)[a-z])/i, $x ) {
print ++$n % 2 ? tr/aeiouAEIOU//dr : $_;
}
This now remembers the actual separators from the original string and leaves alone the first character of the "word" because it's not in the element we will modify.
The code in the foreach doesn't need to use the conditional operator, ?: or some of the other features. The important part is skipping every other element. That split pattern is a bit of a puzzler if you haven't seen it before, but that's what you get with those sorts of requirements. I think modifying a portion of the substring is just as likely to trip up people on a first read.
I mean, if they are going to make you do it the wrong way in the homework, strike back with something that will take up a bit of their time. :)
Oh, this is fun
I had another idea, because tr/// has another task beyond transliteration. It also counts. Because it returns the number of replacements, if you replace anything with itself, you get a count of the occurrences of that thing. You can count vowels, for instance:
my $has_vowels = $string =~ tr/aeiou/aeiou/; # counts vowels
But, with a string of one letter, that means you have a way to tell if it is a vowel:
my $is_vowel = substr( $string, $i, 1 ) =~ tr/aeiou/aeiou/;
You also can know things about the previous character:
my $is_letter = substr( $string, $i - 1, 1 ) =~ tr/a-zA-Z/a-zA-Z/;
Put that together and you can look at any position and know if it's a vowel that follows a letter. If so, you skip that letter. Otherwise, you add that letter to the output:
use v5.10;
$x = "I like apples more than oranges oooooranges\n";
my $output = substr $x, 0, 1; # avoid the -1 trap (end of string!)
for( my $i = 1; $i < length $x; $i++ ) {
if( substr( $x, $i, 1 ) =~ tr/aeiou/aeiou/ ) { # is a vowel
next if substr( $x, $i - 1, 1 ) =~ tr/a-zA-Z/a-zA-Z/;
}
$output .= substr $x, $i, 1;
}
say $output;
This has the fun consequence of using the recommended operator but completely bypassing the intent. But, this is a proper and intended use of tr///.
It appears that you need to put a little more effort into learning Perl before taking on challenges like this. Your example contains a lot of code that simply isn't valid Perl.
$x = "I like apples more than oranges\n"; #the original sentence
foreach $i in #x[1..] {
You assign your text to the scalar variable $x, but then try to use the array variable #x. In Perl, these are two completely separate variables that have no connection whatsoever. Also, in Perl, the range operator (..) needs values at both ends.
If you had an array called #x (and you don't, you have a scalar) then you could do what you're trying to do here with foreach $i (#x)
if $i "AEIOUaeiou";
I'm not sure what you're trying to do here. I guess the nearest useful Perl expression I can see would be something like:
if ($i =~ /^[AEIOUaeiou]$/)
Which would test if $i is a vowel. But that's a regex, so you're not allowed to use it.
Obviously, I'd solve this problem with a regex, but as those are banned, I've reached for some slightly more obscure Perl features in my code below (that's so your teacher won't believe this is your solution if you just cut and paste it):
#!/usr/bin/perl
use strict;
use warnings;
use feature 'say';
my $text = "I like apples more than oranges\n";
# Split the string into an array of words
my #words = split /\s+/, $text;
# For each word...
for (#words) {
# Get a substring that omits the first character
# and use tr/// to remove vowels from that substring
substr($_, 1) =~ tr/AEIOUaeiou//d;
}
# Join the array back together
$text = join ' ', #words;
say $text;
Update: Oh, and notice that I've used tr/AEIUOaeiou//d where you have tr/A E I O U a e i o u//d. It probably won't make any difference here (depending on your approach - but you'll probably be applying it to strings that don't contain spaces) but it's good practice to only include the characters that you want to remove.
We can go over the input string from the end and remove any vowel that's not preceded by a space. We go from right to left so we don't have to adjust the position after each deletion. We don't need to check the very first letter, it shouldn't be ever removed. To remove a vowel, we can use tr///d on the substr of the original string.
for my $i (reverse 1 .. length $x) {
substr($x, $i, 1) =~ tr/aeiouAEIOU//d
if substr($x, $i - 1, 1) ne ' ';
}
Firstly your if statement is wrong.
Secondly this is not a Perl code.
Here is a piece of code that will work, but there is a better way to do it
my $x = "I like apples more than oranges\n";
my $new = "";
my #arr;
foreach my $word (split(' ', $x)) {
#arr = split('', $word);
foreach (my $i; $i<scalar #arr; $i++){
if ($i == 0){
$new .= $arr[$i];
}
elsif (index("AEIOUaeiou", $arr[$i]) == -1) {
$new .= $arr[$i];
}
}
$new .= " ";
}
print "$new\n";
Here I am splitting the string in order to get an array, then I am checking if the given char is a vowel, if it's not, I am appending it to a new string.
Always include
use strict;
use warnings;
on top of your code.
Clearly this is an exercise in lvalues. Obviously. Indubitably!
#!/usr/bin/env perl
# any old perl will do
use 5.010;
use strict;
use warnings;
# This is not idomatic nor fantastic code. Idiotastic?
$_='I am yclept Azure-Orange, queueing to close a query. How are YOU?';
# My little paws typed "local pos" and got
# "Useless localization of match position" :(
# so a busy $b keeps/restores that value
while (/\b./g) {
substr($_,$b=pos,/\b/g && -$b+pos)
# Suggestion to use tr is poetic, not pragmatic,
# ~ tr is sometimes y and y is sometimes a vowel
=~ y/aeiouAEIOU//d;
pos=$b;
}
say
# "say" is the last word.
Was there an embargo against using s/// substitution, or against using all regex? For some reason I thought matching was OK, just not substitution. If matches are OK, I have an idea that "improves" upon this by removing $b through pattern matching side effects. Will see if it pans out. If not, should be pretty easy to replace /\b/ and pos with index and variables, though the definition of word boundary over-simplifies in that case.
(edit) here it is a little more legible with nary a regex
my $text="YO you are the one! The-only-person- asking about double spaces.
Unfortunate about newlines...";
for (my $end=length $text;
$end > 0 && (my $start = rindex $text,' ',$end);
$end = $start-1) {
# y is a beautiful letter, using it for vowels is poetry.
substr($text,2+$start,$end-$start) =~ y/aeiouUOIEA//d;
}
say $text;
Maybe more devious minds will succeed with vec, unpack, open, fork?
You can learn about some of these techniques via
perldoc -f substr
perldoc -f pos
perldoc re
As for my own implementer notes, the least important thing is ending without punctuation so nothing can go after
I'm trying to find the index of white space in a string in Perl.
For example, if I have the string
stuff/more stuffhere
I'd like to select the word "more" with a substring method. I can find the index of "/" but haven't figured out how to find the index of white space. The length of the substring I'm trying to select will vary, so I can't hard code the index. There will only be one white space in the string (other than those after the end of the string).
Also, if anybody has any better ideas of how to do this, I'd appreciate hearing them. I'm fairly new to programming so I'm open to advice. Thanks.
Just use index:
#!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };
my $string = 'stuff/more stuffhere';
my $index_of_slash = index $string, '/';
my $index_of_space = index $string, ' ';
say "Between $index_of_slash and $index_of_space.";
The output is
Between 5 and 10.
Which is correct:
0 1
01234567890123456789
stuff/more stuffhere
If by "whitespace" you also mean tabs or whatever, you can use a regular expression match and the special variables #- and #+:
#!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };
my $string = "stuff/more\tstuffhere";
if ($string =~ m{/.*(?=\s)}) {
say "Between $-[0] and $+[0]";
}
The (?=\s) means is followed by a whitespace character, but the character itself is not part of the match, so you don't need to do any maths on the returned values.
As you stated, you want to select the word between the first /
and the first space following it.
If this is the case, you maybe don't need any index (you need just
the word).
A perfect tool to find something in a text is regex.
Look at the following code:
$txt = 'stuff/more stuffxx here';
if ($txt =~ /\/(.+?) /) {
print "Match: $1.\n";
}
The regex used tries to match:
a slash,
a non-empty sequence of any chars (note ? - reluctant
version), enclosed in a capturing group,
a space.
So after the match $1 contains what was captured by the first
capturing group, i.e. "your" word.
But if for any reason you were interested in starting and ending
offsets to this word, you can read them from $-[1]
and $+[1] (starting / ending indices of the first capturing group).
The arrays #- (#LAST_MATCH_START) and #+ (#LAST_MATCH_END) give offsets of the start and end of last successful submatches. See Regex related variables in perlvar.
You can capture your real target, and then read off the offset right after it with $+[0]
#+
This array holds the offsets of the ends of the last successful submatches in the currently active dynamic scope. $+[0] is the offset into the string of the end of the entire match. This is the same value as what the pos function returns when called on the variable that was matched against.
Example
my $str = 'target and target with spaces';
while ($str =~ /(target)\s/g)
{
say "Position after match: $+[0]"
}
prints
Position after match: 7
Position after match: 18
These are positions right after 'target', so of spaces that come after it.
Or you can capture \s instead and use $-[1] + 1 (first position of the match, the space).
You can use
my $str = "stuff/more stuffhere";
if ($str =~ m{/\K\S+}) {
... substr($str, $-[0], $+[0] - $-[0]) ...
}
But why substr? That's very weird there. Maybe if you told us what you actually wanted to do, we could provide a better alternatives. Here are three cases:
Data extraction:
my $str = "stuff/more stuffhere";
if ( my ($word) = $str =~ m{/(\S+)} ) {
say $word; # more
}
Data replacement:
my $str = "stuff/more stuffhere";
$str =~ s{/\K\S+}{REPLACED};
say $str; # stuff/REPLACED stuffhere
Data replacement (dynamic):
my $str = "stuff/more stuffhere";
$str =~ s{/\K(\S+)}{ uc($1) }e;
say $str; # stuff/MORE stuffhere
Trying to extract the alphanumeric characters from this string:
A_phase_I-II,_open-req_project_id_PX15RAD001
The problem is: the term PX15RAD001 can occur anywhere in the string.
Trying to extract the alpha-numeric part using the below expression. But this returns the entire string. I thought Alum was a valid keyword for alpha-numerics. Is that not the case?
(my $string = $line ) =~ s/\P{Alnum}//g;
print $string;
How can I extract the alphanumeric part of the afore mentioned string?
Thanks in advance.
-simak
At the end as per your input:
> echo "A_phase_I-II,_open-req_project_id_PX15RAD001"|perl -lne 'print $1 if(/id_([A-Z0-9]*)/)'
PX15RAD001
In the middle:
> echo "A_phase_I-II,_open-req_id_PX15RAD001_project" | perl -lne 'print $1 if(/id_([A-Z0-9]*)/)'
PX15RAD001
or in your terms:
$line=~m/id_([A-Z0-9]*)/g;
print $1;
Here are some testcases, produced with the comments of #Vijay s Answer:
my #line = (
'A_phase_I-II,_open-req_project_id_PX15RAD001',
'_PX15RAD001_A_phase_I-II,_open-req_project_id',
'A_pha3333se_I-II,_ope_PX15RAD001_n-req_project',
'A_phase_I-II,_PX15RAD001_open-req_projec123123123t_id',
'A_phase_I-II_PX15RAD001_roject_id'
);
foreach my $string ( #line ) {
$string =~ m{_([^_]{10})_?}g;
print $1 . "\n" if $1;
}
These kinds of questions are hard to answer because there is not enough information. What information we have is:
You say your target string is "alphanumeric", but the entire input string is alphanumeric, except for some punctuation, so that really doesn't tell us anything.
You say it is 12 characters long, but the sample you show is 10 characters long.
You seem to think that "alphanumeric" does not include underscore.
So, the reliable information I can sense from you is:
Target string is always delimited by underscore _
Target string is 10-12 characters, all alphanumeric except underscore.
The "reliable" solution based on this rather skimpy information is:
my $str = "A_phase_I-II,_open-req_project_id_PX15RAD001";
for my $field (split /_/, $str) {
if (length($field) <= 12 and
length($field) >= 10 and # field is 10-12 characters
$field !~ /\W/) { # and contains no non-alphanumerics
# do something
}
}
By splitting on underscore, we can easily isolate each field in the string and perform simpler tests on it, such as the ones above.
I'm working on an XML Document, I need to open it and transform to uppercase some specific tag values on the same line. If I have the same word it only does the substitution for one of them although I'm using two different if loops:
This is my XML:
<pageID="1" width="827" height="1169" Sender_Company="société" Sender_Address="société" Sender_Fax="" Category="C2" Language_2="" Document_Object="" Language_1="french" Language_3="" NumPage="1" Script_1="typed">
This is my code:
while (<FILEIN>) {
if ($_ =~ /pageID="1"/) {
$haschanged = 1;
if ($_ !~ /Sender_Address=""/) {
if ($_ =~ /(Sender_Address="(.*?)")/){
my $SenderAddress = $2;
$SenderAddress = uc($SenderAddress);
$_ =~ s/$1/Sender_Address="$SenderAddress"/;
}
}
if ($_ !~ /Sender_Company=""/) {
if ($_ =~ /(Sender_Company="(.*?)")/) {
my $SenderCompany = $2;
$SenderCompany = uc($SenderCompany);
$_ =~ s/$1/Sender_Company="$SenderCompany"/;
#print "$_\n";
}
}
}
}
When I use two different values for Sender_Company="bla" and Sender_Address="société" the transformation to uppercase works but when I use in this case the same word Sender_Company="société" and Sender_Address="société" it doesn't do the transformation to uppercase.
Does anyone have any ideas? I can't find the logic behind it not wanting to transform the same word when I'm using two distinct if loops at a time. Thank you!
Your understanding of XML is a bit debatable:
That isn't XML. It is an XML fragment at most (Element not closed, tag name can't double as attribute like <pageID="1">, no <?xml ...?> declaration, no root element, …)
Don't parse XML with regexes ;-)
XML doesn't have a concept of “lines”.
Besides of that, the code should work fine. Do note that you can make your life easy, and your code short:
$_ =~ /foo/ is the same as /foo/, $_ !~ /foo/ is the same as !/foo/.
Instead of extracting two captures, and substituting the result in a second regex, you can do it all in just one step:
s{ (?<=Sender_Address=") ([^"]+) (?=") }{ uc $1 }ex
Wait, what? I extract one or more non-"-characters that are preceded by the string Sender_Address=" and are followed by " (look-around assertions). The thing in between I capture, and substitute it with an uppercased version. Because I match at least one character, I don't have to test for the empty tag case. The /e flag allows code in the substitution (not really neccessary here), and the /x allows us to include nonmatching whitespace for better formatting.
You can easily extend this for both attributes you want to uppercase:
# This subsumes your whole logic inside `if (/pageID="1"/)`
$haschanged = 1;
for my $attr (qw/Sender_Address Sender_Company/) {
s{ (?<=\Q$attr\E=") ([^"]+) (?=") }{ uc $1 }ex;
}
The \Q...\E causes the interpolated stuff to match literally, even if it contains characters that would be regex metacharacters otherwise.
There are a few remaining bugs:
You fail to uppercase characters that are given as entities.
XML allows single quotes '...' to be used as tag value delimiters. You don't handle them
See the points under Your understanding of XML…
All of these can be solved by using an XML parser, and then transforming the attributes in the DOM.