You must use some kind of quoting before you can use arbitrary strings in a regex, otherwise the special characters are interpreted as regex constructs instead of regular substrings.

As noted above, you can use either the \Q...\E construct or quotemeta() - it works something like this: 

my $string = 'abc!hu(';
print "\Q$string\E\n";    # prints abc\!hu\(
print quotemeta $string;  # prints abc\!hu\(

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The \Q .. \E construct is a little easier in this case, because you can embed it in your match - you should not use it in the replacement part of a substitution, because that's (a lot like) a regular double-quoted string: 
s/\Q$string\E/$replacement/;

# or ..

$qstring = quotemeta $string;
s/$qstring/$replacement/;

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For (a lot more) info, take a look at 

perldoc perlre
perldoc perlop (the m// part)

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</code> 
-- 
Joost       downtime n. The period during which a system
            is error-free and immune from user input.

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In reply to Re: correct usage of q, quotemeta, with s/// by Joost
in thread correct usage of q, quotemeta, with s/// by cidaris

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