Re^2: Regex as an argument to a sub

Am I doing something wrong? I need two e's, with a modified replacement pattern. Running with two e's on the original replacement gives a compile error.

use strict;
use warnings;

my $test_data = 'This is some test data: $888...!';
my $pattern = qr{(\$?[0-9,]+)};

my $replacement = '<test>$1<\/test>';
my $first_test = apply_regex_e($test_data, $pattern, $replacement);

$replacement = 'q{<test>}.$1.q{<\/test>}';
my $second_test = apply_regex_ee($test_data, $pattern, $replacement);

print $first_test, "\n", $second_test;

sub apply_regex_e {
    my ($data, $pat, $rep) = @_;

    $data =~ s/$pat/$rep/e;
    return $data;
}

sub apply_regex_ee {
    my ($data, $pat, $rep) = @_;

    $data =~ s/$pat/$rep/ee;
    return $data;
}
[download]

Output

This is some test data: <test>$1<\/test>...!
This is some test data: <test>$888<\/test>...!
[download]

Comment on Re^2: Regex as an argument to a sub Select or Download Code

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Re^3: Regex as an argument to a sub by Zaxo (Archbishop) on Sep 23, 2005 at 18:53 UTC
Nope, you're doing it right, I missed a layer of eval. Since the substitute is a string variable containing another variable to interpolate, two evals are needed. After Compline, Zaxo	[reply]
Re^3: Regex as an argument to a sub by ambrus (Abbot) on Sep 24, 2005 at 16:47 UTC
I'm sorry, but I don't really recommend Zaxo's double e solution for serious purposes, as two e modifiers will have to evaluate the code on the right side every time a match is found and the replacement has to be calculated. A double e switch should usually be avoioded, just like a string eval. (If this isn't clear, `s/$pat/$rep/ee` is about the same as `s/$pat/eval($rep)/e`, and here the eval has to be run every time the pattern matches the string.) A better solution would be to pass the replacement as a subroutine, so that the code doesn't have to be compiled multiple times. The first e modifier doesn't have to do this, as the code that generates the replacement string is always the same, so it doesn't have to be recompiled every time a match is found. (Of course, if the replace text is a constant string, you wouldn't need any e's.) (This is of course for the case of your `apply_regex_ee`, where the replacement has to be computed. If the replacement is a constant string, as in `apply_regex_e`, you don't even need a single e, although it doesn't make the solution any worse to have the e switch there.) Here's my version of the code. I'd like to thank chester for the clean example code. use strict; use warnings; my $test_data = 'This is some test data: $888...!'; my $pattern = qr{(\$?[0-9,]+)}; my $replacement = '<test>$1<\/test>'; my $first_test = replace_with_constant($test_data, $pattern, $replacem +ent); my $replacement_func = sub { "<test>" . $1 . "<\/test>"; }; # OR my $replacement_func = sub { "<test>$1<\/test>"; }; my $second_test = replace_with_dynamic($test_data, $pattern, $replacem +ent_func); print $first_test, "\n", $second_test, "\n"; sub replace_with_constant { my ($data, $pat, $rep) = @_; $data =~ s/$pat/$rep/; # OR $data =~ s/$pat/$rep/e; return $data; } sub replace_with_dynamic { my ($data, $pat, $rep) = @_; $data =~ s/$pat/&$rep()/e; return $data; } [download] Update 2009 april 1: this seems to be a common question, Regular expression "replace string interpolation" problem asks it again.	[reply] [d/l] [select]