{1} is redundant in a regex - always.

Your indentation is stuffed. It looks like the first if is inside the first while loop - it isn't.

redo FILENAME doesn't have a matching loop.

You could structure your code something like:

while (1) {
    while ($out !~ m/^[sSfF]$/) {
        ...
    }
    
    if ($out =~ m/^[sS]$/) {
        print $output;
        next;
    }
    
    last;
}

exit if $out !~ m/^[fF]$/;

while (1) {
    while ($save !~ (m/^[a-zA-Z]\w*$/)) {
        ...
    }
    
    if (-e $save) {
        ...
    }
    
    if ($overwrite =~ m/^[nN]$/) {
        next;
    }
    
    ...
    last;
}
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