#!/usr/bin/env perl

use warnings;
use strict;

while (<DATA>) {
    print $2 . "\n" if /(\d)\st=(\w+)/;
}

__DATA__
0
1 t=something
2 t=3foo7bar

[download]
Creates the following output: 
something
3foo7bar

[download]
Is this what you are trying to achieve? In any case, you should heed Limbic~Region's advice on understanding character classes (what goes into square brackets in a regex.)

In reply to Re^2: string selection from a character class by toolic
in thread string selection from a character class by karden

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