But most importantly I am looking for a way to exit when it hits the output "press the enter key to stop..."

Seems likely that the simplest solution might be to just kill the process;

my $pid = open SSH, '-|', qw[ ssh -l gmon 3par-S400 statvv -ni ] or di
+e $!;

my @lines;
push @lines, $_ while ( $_ = <SSH> ) !~ m[Press the enter key to stop.
+..];
kill 9, $pid;

## process data
[download]

Whether it is acceptable to kill an SSH session, and whether that will properly clean up the remote process and session you'll have to look up your docs or try it to find out.