I have 2 input files. One is a list of prefix and lengths, like this:

101xxx
102xxx
30xx
31xx

(where x is any number)

And another is a list of numbers.

I want to iterate through the second file, matching each number against any of the prefix/lengths. This is fairly easy. I build a list of regexps:

my @regexps = ('101...', '102...', '30..', '31..');

Then:

foreach my $regexp (@regexps) {
    if (/$regexp/) {
        # do something

But, as you can guess, this is slow for a long list.

I could convert this to a single regexp:

my $super_regexp = '101...|102...|30..|31..';

...but, what I need is to know which regexp matched the item, and what the ..s matched.

I tried this:

my $catching_regexp = '(101)(...)|(102)(...)|(30)(..)|(31)(..)';

but then I don't know whether to look in $1, $3, %5 or $7.

Any ideas? How can I match against any of these prefix/lengths and know which prefix, and what the remaining digits where?