$str = "text delimeter text delimeter text";
@a = split(/\s+(delimeter)\s+/, $str);
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Note that this won't work if the delimiter (called "delimeter" here :) is at the end or at the beginning of your string.
probably, replacing the \s+ with \s* in the regexp would be better. But then, if "delimeter" was at the beginning of the string, you'd have an empty string as the first element of your array.