How do I handle special characters in a Perl regex?

I'm using a Perl program to extract text from a file. I have an array of strings which I use as delimiters for the text, e.g:

$pat = $arr[1] . '(.*?)' . $arr[2];

if ( $src =~ /$pat/ ) {
   print $1;
}

However, two of the strings in the array are $450 and (Buy now). The problem with these is that the symbols in the strings represent end-of-string and capture group in Perl regular expressions, so the text doesn't parse as I intend.

Is there a way around this?

Try Perl's quotemeta function. Alternatively, use \Q and \E in your regex to turn off interpolation of values in the regex. See perlretut for more on \Q and \E - they may not be what you're looking for.

quotemeta escapes meta-characters so they are interpreted as literals. As a shortcut, you can use \Q...\E in double-quotish context to surround stuff that should be quoted:

$pat = quotemeta($arr[1]).'(.*?)'.quotemeta($arr[2]);
if($src=~$pat) { print $1 }

or

$pat = "\Q$arr[1]\E(.*?)\Q$arr[2]";  # \E not necessary at the end
if($src=~$pat) { print $1 }

or just

if ( $src =~ /\Q$arr[1]\E(.*?)\Q$arr[2]/ ) { print $1 }

Note that this isn't limited to interpolated variables; literal characters are affected too:

perl -wle'print "\Q.+?"'
\.\+\?

though obviously it happens after variable interpolation, so "\Q$foo" doesn't become '\$foo'.

Use quotemeta:

$pat = quotemeta($arr[1]) . '(.*?)' . quotemeta($arr[2]);
if ($src =~ $pat) 
    print $1;