Hello WTem, and welcome to the Monastery!

To remove all occurrences of a given string (in this case, the character /), use the substitution operator s/// together with the /g modifier:

12:39 >perl -wE "my $interface = 'POS1/0/0'; $interface =~ s{/}{}g; sa
+y $interface;"
POS100

12:39 >
[download]

See perlop#Regexp-Quote-Like-Operators and “Global matching” in perlretut.

Hope that helps,