My first thought was that you should be able to use signals to catch these types of floating point exceptions...

$SIG{FPE}=sub{...};
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...but it turns out that perl is too smart and catches these types of errors before passing them on to the hardware. Does anyone know if there is a compiler flag for perl which would disable these checks? Just for the fun of it I compiled up a version of perl which commented out the divide by zero check (in pp.c)...

    /*if (right == 0.0)
      DIE(aTHX_ "Illegal division by zero");*/
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...make, compile, run...

$ ./perl -e '$a=1.23/0.00;print "\$a=$a\n"'
$a=inf
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...looks like we're going down the right track...

    if (right == 0.0)
        PUSHs(&PL_sv_undef);/*DIE(aTHX_ "Illegal division by zero");*/
    else
        PUSHn( left / right );
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...make, compile, rerun...

$ ./perl -e 'print "UNDEFINED\n" unless (defined(1.23/0.00))'
UNDEFINED
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Of course you'd probably want to take care of the integer division case also.