What you want is a loop. Perl has several different kinds of loop - for, foreach, while, until, etc. They all boil down to the same thing, but depending on what you're doing, one type of loop might be more convenient than then other.

use v5.12;
use strict;
use warnings;

# Obscure but easy way of reading a file into a string to match agains
+t...
$_ = do { local (@ARGV, $/) = 'loop.txt'; <> };

# Extract text we're interested in...
my @matches = m{<a>(.+?)</a>}sg;

# Loop through the matches...
foreach my $match (@matches)
{
    # This block gets executed for each match!
    say "GOT: $match";
}
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