The trick lies in the fact that you want to match any character, but that the dot looses its special meaning in the square brackets. See perlop and perlre. You could just replace the bracket stuff with a single dot.

I would prefer to use substr to get the data (untested, you get the idea mehopes):

my @lengths = qw/1 20 20 5/;
#inside some looplike thing
  my @array = ();
  push @array, substr( $line, 0, $_, '' ) for @lengths;
  print join "\t", @array;
}
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Hope this helps,

Jeroen
"We are not alone"(FZ)
Update: Just stick to unpack as Hofmator says. It gives you all in one line:

my @array= unpack 'a1a20a20a5', $line;
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I couldn't get it to strip trailing spaces/nulls with A or Z or @, though.