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\(
[download]

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/;
[download]

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

perldoc perlre
perldoc perlop (the m// part)
[download]

</code>

-- 
Joost       downtime n. The period during which a system
            is error-free and immune from user input.
[download]