Nice. Tiny changes, though... want nth char, not (n+1)th... also, you want \s+, not \s*... and might as well decide that by "word" we mean a run of non-whitespace (that is... probably a bad idea to mix \w and \S... so I'll just go with \S).

[me@host bin]$ perl -we '$n = $ARGV[0]; $_ = "a b csadf sdfas ddd"; /(
+?:\S+\s+){@{[$n-1]}}(\S+)/; print "$1\n"' 1
a
[me@host bin]$ perl -we '$n = $ARGV[0]; $_ = "a b csadf sdfas ddd"; /(
+?:\S+\s+){@{[$n-1]}}(\S+)/; print "$1\n"' 2
b
[me@host bin]$ perl -we '$n = $ARGV[0]; $_ = "a b csadf sdfas ddd"; /(
+?:\S+\s+){@{[$n-1]}}(\S+)/; print "$1\n"' 4
sdfas
[me@host bin]$
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