The function only returns undef in that instance. I hate having some generic function die on me unexpectedly, especially when my boss calls me up shouting "You're stoopid program doesn't work!" I'd rather leave the choice to the calling program:

callexternalpgm( parms ) or die "$!";
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or, more likely,

callexternalpgm( parms ) or LogIt( "Error calling external program: $!
+" );
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