shift keeps on reducing the number of elements in @ARGV in the second instance. Thus the while loop (via -n option) ends eventually. See perldoc perlrun, and Deparse ... 

perl -MO=Deparse -ne ' map { print $_ , "\n" if ( -d $_ )  ; } @ARGV  
+'
LINE: while (defined($_ = <ARGV>)) {
    map {print $_, "\n" if -d $_;} @ARGV;
}
-e syntax OK

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In reply to Re: ls piped tpo perl -pe runs indefintely by Anonymous Monk
in thread ls piped tpo perl -pe runs indefintely by ISAI student

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