Well, I would use \b,

say "$_: ", /\b(10000|[1-9][0-9]{0,3})\b/ ? "Y" : "N"
        for qw{240 2 3600 1 10000 0 0000 19999 999999999};
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Same as your result:

240: Y
2: Y
3600: Y
1: Y
10000: Y
0: N
0000: N
19999: N
999999999: N
[download]

updated: made capturing group