Well, I'm not sure about the conventions but I have gotten used to returning 1 for success or 0 for fail. That way I can easily do something like..

if(&mysubroutine()) {
    ...
    #continue as mysubroutine was successful
}
else {
    ...
    Something in mysubroutine failed
}

sub mysubroutine()
{
    my $rc = 0; 
    #this is returned if $rc is not modified which indicates a failure
+...
    
    #as a silly example we will open a file
    if (open FH, "<./test.txt") {
        ...
        #read in file as the open was successful
        $rc = 1;
    }
    return($rc);
}
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