in reply to Need a regular expression to check the first digit

Further to GrandFather's remarks:   The regex /^[5]+$/ does not match the string '503009496', but is there any other string it would match? What about the strings

5 55 555 555555555

If you find some strings that match, how would they and the strings you know do not match interact with the regex components mentioned by GrandFather? Please see perlre, perlretut, perlrequick and perlreref.

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