$ ls *.txt
javastuff.txt  modules.txt
$ perl -le '$,=" "; print glob "*.txt"'
javastuff.txt modules.txt
$ perl -le '$,=" "; print glob "joe.txt"'
joe.txt
$ perl -le '$,=" "; print glob "joe.txt*"'

$ perl -le 'print ((-e "joe.txt")?"yes":"no")'
no
$ perl -le 'print ((-e "*.txt")?"yes":"no")'
no
$ perl -le 'print ((-e "modules.txt")?"yes":"no")'
yes
$