The reason tachyon's version doesn't work is not because of removing the 347, but because he golfed away the localisation of $_.

P:\test>type junk.pl
sub is_rotatable{
#234567890123456789012345678901234567
$_=$_[0];y/2569347/5296/;pop==reverse
}

printf "%s %s rotatable\n", $_, is_rotatable( $_ ) ? 'is' : 'not'
        for 33, 131, 141, 171,
        25696925, 101, 88;


P:\test>junk
Modification of a read-only value attempted at P:\test\junk.pl line 3.
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