Do we ever have perfect data? I prefer to use a test to warn about invalid data. The following code (untested) makes use of runtime switches (ref: perldoc perlrun). Use -p for the I/O and -i for backup.

#!perl -p -ibak
if (!s/^g(Ord_\d{4}\.png)\s*$/$1/) {
    warn "Invalid line: $_\n";
    $_ = <>;
    redo;
}
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