my $contextual = '(?:c(?:bex|e(?:bax|vpxf?)|hff(?:vrf|l)|vff(?:\\ gnxr|\\-gnxr|gnxr|r(?:ef|[feq])|vat|l)?)|dhvzf?|ebbg(?:r(?:ef|[eq])|vat|f)?|f(?:bq(?:q(?:rq|vat)|f)?|chax|perj(?:rq|vat|f)?|u(?:nt(?:t(?:r(?:ef|[qe])|vat)|f)?|vg(?:g(?:r(?:ef|[qe])|vat|l)|r(?:ef|[fqel])|vat|[fr])?))|g(?:heqf?|jngf?|vgf?)|jnax(?:r(?:ef|[eq])|vat|f)?|n(?:ef(?:r(?:\\ ubyr|\\-ubyr|ubyr|[fq])|vat|r)|ff(?:\\ ubyrf?|\\-ubyrf?|rq|ubyrf?|vat))|o(?:ba(?:r(?:ef|[fe])|vat|r)|h(?:ttre|yy(?:\\ fuvg(?:g(?:r(?:ef|[qe])|vat)|f)?|\\-fuvg(?:g(?:r(?:ef|[qe])|vat)|f)?|fuvg(?:g(?:r(?:ef|[qe])|vat)|f)?))|n(?:paco|yy(?:r(?:ef|[qe])|vat|f)?)|yb(?:bql|j(?:\\ wbof?|\\-wbof?|wbof?)))|p(?:bpx(?:\\ fhpx(?:ref?|vat)|\\-fhpx(?:ref?|vat)|fhpx(?:ref?|vat)|f)?|enc(?:c(?:r(?:ef|[eq])|vat|l)|f)?|h(?:agf?|z(?:vat|zvat|f)))|q(?:batf?|vpx(?:\\ urnq|\\-urnq|rq|urnq|vat|yrff|f)?)|s(?:hpx(?:rq|vat|f)?|neg(?:r[eq]|vat|[fl])?|rygpu(?:r(?:ef|[efq])|vat)?)|u(?:hzc(?:r(?:ef|[eq])|vat|f)?|n(?:eq[\\-\\ ]?ba|ys(?:\\ n[fe]|\\-n[fe]|n[fe])frq))|z(?:bgure(?:\\ shpx(?:ref?|vat)|\\-shpx(?:ref?|vat)|shpx(?:ref?|vat))|hgu(?:n(?:\\ shpx(?:ref?|vat|[nnn])|\\-shpx(?:ref?|vat|[nnn])|shpx(?:ref?|vat|[nnn]))|re(?:\\ shpx(?:ref?|vat)|\\-shpx(?:ref?|vat)|shpx(?:ref?|vat)))|reqr?))';