perl -E"say(),open $fh[$_], '>', qq[file$_] or die $! for 1 .. 1e5"
1
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...
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Too many open files at -e line 1.

##</code><code>##

open $fh, .... or die ...;
close $fh;

##</code><code>##

open $fh, ... and printf( LOG "%s(%u) opening %u\n", __FILE__, __LINE__, fileno( $fh ) ) or die ...;
printf( LOG "%s(%u) closing %u\n", __FILE__, __LINE__, fileno( $fh ) ) and close $fh;