Nested foreach loop not working - perl

Question

It should be a simple nested foreach loop but it's not working and really starting to annoy me that I can't figure this out! Still a perl beginner but I thought I understood this by now. Can someone explain to me where I'm going wrong? The idea is simple: 2 files, 1 small, 1 large with info I want in the small one. Both have unique id's in them. Compare and match the id's and output a new small file with the added info in the small file.
I have 2 pieces of code: 1 without stricts and 1 with and both are not working. I know to use stricts but i'm still curious as to why the one without stricts isn't working either.
WITOUT STRICTS:
if ($#ARGV != 2){
print "input_file1 input_file2 output_file\n";
exit;
}
$inputfile1=$ARGV[0];
$inputfile2=$ARGV[1];
$outputfile1=$ARGV[2];
open(INFILE1,$inputfile1) || die "No inputfile :$!\n";
open(INFILE2,$inputfile2) || die "No inputfile :$!\n";
open(OUTFILE_1,">$outputfile1") || die "No outputfile :$!\n";
$i = 0;
$j = 0;
#infile1=<INFILE1>;
#infile2=<INFILE2>;
foreach ( #infile1 ){
#elements = split(";",$infile1[$i]);
$id1 = $elements[3];
print "1. $id1\n";
$lat = $elements[5];
$lon = $elements[6];
$lat =~ s/,/./;
$lon =~ s/,/./;
print "2. $lat\n";
print "3. $lon\n";
foreach ( #infile2 ){
#loopelements = split(";",$infile2[$j]);
$id2 = $loopelements[4];
print "4. $id2\n";
if ($id1 == $id2){
print OUTFILE_1 "$loopelements[0];$loopelements[1];$loopelements[2];$loopelements[3];$loopelements[4];$lat,$lon\n";
};
$j = $j+1;
};
#elements = join(";",#elements); # add ';' to all elements
#print "$i\r";
$i = $i+1;
}
close(INFILE1);
close(INFILE2);
close(OUTFILE_1);
The error without is the second loop will not start if i'm not mistaken.
WITH STRICTS:
use strict;
use warnings;
my $inputfile1 = shift || die "Give input!\n";
my $inputfile2 = shift || die "Give more input!\n";
my $outputfile = shift || die "Give output!\n";
open my $INFILE1, '<', $inputfile1 or die "In use/Not found :$!\n";
open my $INFILE2, '<', $inputfile2 or die "In use/Not found :$!\n";
open my $OUTFILE, '>', $outputfile or die "In use/Not found :$!\n";
my $i = 0;
my $j = 0;
foreach ( my $infile1 = <$INFILE1> ){
my #elements = split(";",$infile1[$i]);
my $id1 = $elements[3];
print "1: $id1\n";
my $lat = $elements[5];
my $lon = $elements[6];
$lat =~ s/,/./;
$lon =~ s/,/./;
print "2: $lat\n";
print "3: $lon\n";
foreach ( my $infile2 = <$INFILE2> ){
my #loopelements = split(";",$infile2[$j]);
my $id2 = $loopelements[4];
print "4: $id2\n";
if ($id1 == $id2){
print $OUTFILE "$loopelements[0];$loopelements[1];$loopelements[2];$loopelements[3];$loopelements[4];$lat,$lon\n";
};
$j = $j+1;
};
##elements = join(";",#elements); # add ';' to all elements
#print "$i\r";
$i = $i+1;
}
close($INFILE1);
close($INFILE2);
close($OUTFILE);
The error with stricts:
Global symbol "#infile1" requires explicit package name at Z:\Data-Content\Data\test\jan\bestemming_zonder_acco\add_latlon_dest_test.pl line 16.
Global symbol "#infile2" requires explicit package name at Z:\Data-Content\Data\test\jan\bestemming_zonder_acco\add_latlon_dest_test.pl line 31.

Answer 1

Your 'strict' implementation gives you errors due to a confusion about the sigils (the $ and # characters) indication whether a variable is an scalar or an array. In the loop statement you are reading each line of the file into a scalar called $infile1 but in the following line you are trying to access a element of the array #infile1. These to variables are not related and as perl tells you the latter is not declared.
Another problem with you 'strict' implementation is that you are reading the file inside the loop. This means that for nested loops you will read file 2 in the first iteration of the outer loop and for all succeeding iterations the inner loop will not be able to read any lines.
I missed the foreach/while issue, pointed out by stevenl, even fixing the stricture issues will leave you with foreach loops with only one iteration.
I'm not sure what your problem with the unstrict script are.
But I wouldn't use a nested loop at all for processing two files. I would un-nest the loops, so it roughly looked like this:
my %cord;
while ( my $line = <$INFILE1> ) {
my #elements = split /;/, $line;
$cord{ $elements[3] } = "$elements[5],$elements[6]";
}
while ( my $line = <$INFILE2> ) {
my #elements = split /;/, $line;
if ( exists %coord{ $elements[4] } ) {
print $OUTFILE "....;$cord{ $elements4 }\n";
}
}

Answer 2

I can't see exactly where the problem with the non-strict version is. What is the problem that you are encountering?
The problem with the strict version is particularly in these 2 lines:
foreach ( my $infile1 = <$INFILE1> ){
my #elements = split(";",$infile1[$i]);
You have a scalar $infile1 in the first line, but you are treating it as an array in the next line. Also, change the foreach to a while (see below).
A few comments.
For the non-strict version, you could have collapsed the loop to a C-style for loop as:
for (my $i = 0; $i < #infile1; $i++) {
...
}
That can be made simpler to read if you go without the array indexes altogether:
foreach my $infile1 (#infile1) {
my #elements = split ';', $infile1;
...
}
But with the larger file, it might take time to slurp the entire file into the array at the beginning. So it might be better to iterate through the file as you go:
while (my $infile = <$INFILE1>) {
...
}
Note the last point should be how the strict version looks. You need a while loop rather than a foreach loop, because assigning <$INFILE1> to a scalar means it will return the next line only, which evaluates to true as long as there is another line in the file. (Thus, the foreach would only ever get the first line to loop over.)

Answer 3

You don't reset $j before the inner foreach loop runs. Therefore, the second time your inner loop runs, you are trying to access elements that are past the end of the array. This mistake exists in both the strict and non-strict version.
You should not be using $i and $j at all; the point of foreach is that it automatically gets each element for you. Here is an example of correctly using foreach in the inner loop:
foreach my $line ( #infile2 ){
#loopelements = split(";",$line);
#...now do stuff as before
}
This puts each element of #infile one into the variable $line in succession, until you have gone through all of the array.