I'm not very familiar with Linux environments, but here's my guess as to what's happening.

The back ticks are similar to system in that it runs the command and waits for the command to return control before allowing the script to continue. I believe what is happening is that the gnome-terminal is launching a new terminal console and is providing it $cmd's value and then is immediately returning control, which is why your script is not waiting after issuing the command.

I'd recommend one of the following.

• Modify the last line to be: my $res = `$cmd`; -- This skips opening in a new console and your script will wait for mount to return control before continuing.
• From Perl, issue the mount command with no options inside back ticks. This will provide you with a list of mounted mount points. If /home/customer/mnt is not listed, then you don't have it mounted.
• Use something like IPC::Open3 to be able to run the mount command and to be able to read in from STDOUT and STDERR.