perl -ape 'substr($_,0,length $l) =~ tr/ / /c if $F[0] eq $l;$l=$F[0]' <<END
GEORGE 21
GEORGE 45
NICK   12
PETER  27
JIM    18
JIM    87
CHRIS  33
END

##</code><code>##

GEORGE 21
       45
NICK   12
PETER  27
JIM    18
       87
CHRIS  33