What have you tried? What didn't work? See How do I post a question effectively?.

A regular expression will likely do what you want:

my $string  = 'examplestringofrandomlength/userid=6&refid=49';
my ($num1, $num2) = $string =~ /\d+/g;
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See perlretut, in particular Using regular expressions in Perl.

Note that given the simplicity of this expression, it can fail in many ways - for example, if your string is really stringwithnumber111/userid=6&refid=49, you'll get the wrong result. If this is an issue, post a more accurate and complete set of sample strings.