regex matching on metacharacters

slugger415 has asked for the wisdom of the Perl Monks concerning the following question:

Hi all, sorry if this is a naive question but I've searched around the web and haven't found a good answer, including https://perldoc.perl.org/perlre#Metacharacters.

How do I match a regex that contains metacharacters that are used in matching, such as asterisks, parens, etc.? Without escaping each?

I have two variables set, both containing asterisks, and a regex comparison:

#! /usr/bin/perl
my $v1 = "*hello";
my $v2 = "*hello";

if ($v1 =~ /$v2/){
 print "match\n";    
}
[download]

This obviously results in a Quantifier follows nothing in regex error. I can escape out the asterisk and it works fine:

$v2 =~ s/\*/\\\*/g;
[download]

But is there a more elegant way to do that, one that might also pick up some of the others?

thanks

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Re: regex matching on metacharacters by LanX (Saint) on Jul 21, 2022 at 00:06 UTC
> But is there a more elegant way to do that, one that might also pick up some of the others? yes, see `quotemeta` resp. `\Q` and `\E` ° demo `>perl $v1 = "hello"; $v2 = "hello"; print quotemeta($v2),"\n"; print "match" if $v1 =~ /\Q$v2/; __END__ \*hello match >` [download] Cheers Rolf _{(addicted to the Perl Programming Language :) Wikisyntax for the Monastery} °) also `perlre#Quoting-metacharacters`	[reply] [d/l]
Re^2: regex matching on metacharacters by slugger415 (Monk) on Jul 21, 2022 at 03:32 UTC
thank you!	[reply]
Re: regex matching on metacharacters by hippo (Archbishop) on Jul 21, 2022 at 09:15 UTC
Do you really want a regex match or are you actually trying to perform a substring match? If the latter, then consider index instead. `#!/usr/bin/env perl use strict; use warnings; my $str = 'You say hello, but you mean goodbye.'; my $substr = '*hello'; print "match\n" if index ($str, $substr) > -1;` [download] 🦛	[reply] [d/l]