system "strace -o /tmp/strace.out -e open,read more @ARGV";

open my $trace, "/tmp/strace.out" or die;

my $last = '';

while (<$trace>) {
    if (/read\(2,\s*"(.*)",\s*1\)\s*=\s*1$/) {
        $last = $1;
    }
}

print "exited with key >$last<\n";
[download]

But it is so weak...

update: How about Ctrl-C?

system "strace -o /tmp/strace.out -e open,read more @ARGV";
open my $trace, "/tmp/strace.out" or die;
my $last = '';
while (<$trace>) {
    if (/read\(2,\s*"(.*)",\s*1\)\s*=\s*1$/ or /--- SIG(\w+)/) {
        $last = $1;
    }
}
print "exited with key >$last<\n";
[download]