while (<DATA>) {
  print "$&\n" if ($_=~/^\/(.+)modem$/);
}


__DATA__
/1sbc/dasds/sdf/dsd/modem
/2sbc/dasds/FSFsdf/dsd/modem1
/3sbc/dasdFDAs/sFDASFdf/dsd/modem
/4sbc/dasFSDAds/sdf/dFDsd/modem3