If you don't need to process the output in the perl program: 
open PROG,"|/some/program" or die "Can't fork program: $!";
print PROG "input line 1\n";
print PROG "input line 2\n";
close PROG;

[download]
Should do it. See perlopentut.

For interactive sessions, see Expect and IPC::Open3 or IPC::Open2

"What should it profit a man, if he should win a flame war, yet lose his cool?"

In reply to Re: running an interactive only program using perl by Joost
in thread running an interactive only program using perl by Angharad

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