Here's a rather simple solution that may work for you.

#! perl -slw
use strict;

our $WAIT ||= 10;

my $cmd = 'perl -e"$|++;sleep 1, print for 1 .. 10" |';
my $pid = open my $cmdFh, $cmd or die "Couldn't run '$cmd': $!";

sleep 1 while kill 0, $pid and $WAIT--;
kill 3, $pid and warn 'Command timed out' if $WAIT;

my $results = do{ local $/; <$cmdFh> };
print "Got: '$results'";
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A few simple tests

c:\test>junk9 -WAIT=2
Command timed out at c:\test\junk9.pl line 11.
Got: '12'

c:\test>junk9 -WAIT=9
Command timed out at c:\test\junk9.pl line 11.
Got: '12345678'

c:\test>junk9 -WAIT=10
Got: '12345678910'

c:\test>junk9 -WAIT=11
Got: '12345678910'
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