#!perl -i.bak
my @input =  <>;
if (!scalar grep {/Friday/} @input) {
    splice @input, 1, 0, "Friday\n";
}
print @input;

##</code><code>##


perl -v
This is perl 5, version 30, subversion 2 (v5.30.2) built for MSWin32-x64-multi-t
hread