$status = system( "$program arg1 $arg2" );

##</code><code>##

open( SH, "| /bin/csh" ) or die "Can't start subshell: $!";
print SH "echo this is foo bar\n";
print SH "source some_script\n";
print SH "echo \$some_obscure_shell_variable_set_by_some_script\n";
#...