Suggestions for eqnalign

The following packages have something in common with the package eqnalign. The packages are ordered in decreasing similarity.

Package eqnarray: More generalised equation arrays with numbering
Package odesandpdes: Optimizing workflow involving odes and pdes
Package cases: Numbered cases environment
Package subeqnarray: Equation array with sub numbering
Package spalign: Typeset matrices and arrays with spaces and semicolons as delimiters
Package systeme: Format systems of equations
Package witharrows: Aligned math environments with arrows for comments
Package phfthm: Goodies for theorems and proofs
Package inkpaper: A mathematical paper template
Package mhs: Historical mathematics
Package atendofenv: Add a custom symbol at the end of an environment
Package jmsdelim: A package for compositional delimiter sizing
Package resmes: Measure restriction symbol in LaTeX
Package skmath: Extensions to the maths command repertoir
Package boldtensors: Bold latin and greek characters through simple prefix characters
Package bropd: Simplified brackets and differentials in LaTeX
Package conteq: Typeset multiline continued equalities
Package correctmathalign: Correct spacing of the alignment in expressions
Package cascade: Constructions with braces to present mathematical demonstrations
Package complexpolylongdiv: Typesetting (complex) polynomial long division
Package delim: Simplify typesetting mathematical delimiters
Package delimseasy: Delimiter commands that are easy to use and resize
Package fixdif: Macros for typesetting differential operators
Package flagderiv: Flag style derivation package
Package freemath: LaTeX maths without backslashes
Package lplfitch: Fitch-style natural deduction proofs
Package mhequ: Multicolumn equations, tags, labels, sub-numbering
Package mdwmath: Some maths extensions
Package mathsemantics: Semantic math commands in LaTeX
Package matc3mem: Class for MatematicaC3 textbooks
Package mathstyle: Manage mathematics typesetting style