Try this ...

bash-2.05b$ cat readkey.pl
#!/usr/bin/perl
use Term::ReadKey;
 
ReadMode 4; # Turn off controls keys
while (not defined ($key = ReadKey(-1))) {}
print "Get key $key\n";
ReadMode 0; # Reset tty mode before exiting
bash-2.05b$ ./readkey.pl
Get key 7
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You may have to install TermReadKey I installed version 2.14. 2.21 didn't work for me for some reason? I am running Redhat 9 / Perl 5.8.