How can I use 's///' if my string contains a '/'? - perl

Question

I'm using Perl 5.10.6 on Mac 10.6.6. I want to execute a simple search and replace against a file so I tried:
my $searchAndReplaceCmd = "perl -pi -e 's/\\Q${localTestDir}\\E//g' ${testSuiteFile}";
system( $searchAndReplaceCmd );
but the problem above is the variable $localTestDir contains directory separators ("/"), and this screws up the regular expression ...
Bareword found where operator expected at -e line 1, near
"s/\Q/home/selenium"
Backslash found where operator expected at -e
line 1, near "Live\" syntax error at -e line 1, near
"s/\Q/home/selenium"
Search pattern not terminated at -e line 1.
How do I do a search and replace on a file when the variable in question contains regular expression characters? Thanks.

Answer 1

It seems that $localTestDir has begins with a /.
Remedy by changing the regex delimiter to something other than /:
my $searchAndReplaceCmd = "perl -pi -e 's!\\Q${localTestDir}\\E!!g' ${testSuiteFile}";
From perldoc perlrequick :
$x = "A 39% hit rate";
$x =~ s!(\d+)%!$1/100!e; # $x contains "A 0.39 hit rate"
The last example shows that s/// can use other delimiters, such as
s!!! and s{}{}, and even s{}//. If single quotes are used s''', then
the regex and replacement are treated as single-quoted strings.

Answer 2

Question is why you do a search and replace from within perl, through the shell, within perl. Seems like a roundabout way of doing things, and you'll run into problems with shell interpolation.
The \Q ... \E should override the special characters in your string, so / "should" not be an issue. From perlre:
\Q quote (disable) pattern metacharacters till \E
Here's an alternative (untested), all perl solution. If you want to be extra certain, exchange the / delimiter to something else, such as s### (you can use any character as a delimiter).
use strict;
use warnings;
use File::Copy;
open my $fh, '<', $testSuiteFile or die $!;
open my $out, '>', $testSuiteFile . ".bak" or die $!;
while (<$fh>) {
s/\Q${localTestDir}\E//g;
print $out $_;
}
move($testSuiteFile . ".bak", $testSuiteFile) or die $!;
Or use Tie::File
use strict;
use warnings;
use Tie::File;
tie, my #file, 'Tie::File', $testSuiteFile or die $!;
for (#file) {
s/\Q${localTestDir}\E//g;
}
untie #file;

Answer 3

Changing the delimiters is useful, but more generally you can put a backslash in front of any regular expression character to make it non-special.
So s/\/abc/\/xyz/ will work, although it is not very readable.

Answer 4

The problem is that the substitution of $localTestDir is happening too soon.
Here is an approach that lets you use / for your re-delimiters:
system('perl', '-pi',
'-e', 'BEGIN { $dir = shift(#ARGV) };',
'-e', 's/\\Q$dir\\E//g',
$localTestDir,
$suiteTestFile
);
Note that this also protects the contents of $suiteTestFile from being interpreted by the shell.