Rails Regexp::IGNORECASE while matching exact options with number options also included in the results

I want to match the options between two arrays with exact string.

options = ["arish1", "arish2", "ARISH3", "arish 2", "arish"]
choices = ["Arish"]
final_choice = options.grep(Regexp.new(choices.join('|'), Regexp::IGNORECASE))
p final_choice

Output:
 ["arish1", "arish2", "ARISH3", "arish 2", "arish"]

but it should be only match "arish"

You need to use

final_choice = options.grep(/\A(?:#{Regexp.union(choices).source})\z/i)

See the Ruby online demo.

Note:

• A regex literal notation is much tidier than the constructor notation
• You can still use a variable inside the regex literal
• The Regexp.union method joins the alternatives in choices using | "or" regex operator and escapes the items as necessary automatically
• \A anchor matches the start of stirng and \z matches the end of stirng.
• The non-capturing group, (?:...), is used to make sure the anchors are applied to each alternative in choices separately.
• .source is used to obtain just the pattern part from the regex.