First, use the qq() or q() function instead of escaping quotes:

$test = qq[some_text="asdfasdftest.123"];
# or, because you weren't interpolating:
$test = 'some_text="asdfasdftest.123"';
[download]

Next, to deal with mulitple matches:

# untested.
@extensions = qw( 123 456 );
$match = join '|', @extensions;
if ( $test =~ /($match)$/ )
# etc
[download]

--Bob Niederman, http://bob-n.com

All code given here is UNTESTED unless otherwise stated.