String#{delete,tr}
"hello".delete "l","lo" #=> "heo"
"hello".delete "lo" #=> "he"
"hello".delete "aeiou", "^e" #=> "hell"
"hello".delete "ej-m" #=> "ho"
"hello".tr('el', 'ip') #=> "hippo"
"hello".tr('a-y', 'b-z') #=> "ifmmp"
"hello".tr('^aeiou', '*') #=> "*e**o"
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